Electro-optical techniques have been employed for measuring sidewall thickness of transparent containers. For example, U.S. Pat. No. 6,806,459 discloses an apparatus and method for measuring sidewall thickness of a container, which includes a conveyor for moving the container transversely of its axis through an inspection station while simultaneously rotating the container around its axis by “rolling” the container along a rail at the inspection station. A light source and an illumination lens system direct onto the sidewall of the container a line-shaped light beam having a long dimension perpendicular to the axis of the container, parallel to the direction of movement through the inspection station and of sufficient length to illuminate the container sidewall as it is rolled along the rail at the inspection station. An anamorphic imaging lens system directs onto a light sensor light energy reflected from portions of the outside and inside sidewall surfaces that are perpendicular to the illumination light energy. An information processor is responsive to light energy directed onto the light sensor by the imaging lens system for determining the thickness of the container between the outside and inside sidewall surfaces as the container is rolled along the rail. Although the apparatus and method disclosed in the noted patent are well suited for measuring sidewall thickness of round containers, such apparatus and method are not well suited for measuring sidewall thickness of non-round containers that cannot be made to roll along the rail at the inspection station.
U.S. Pat. No. 5,291,271 discloses an apparatus and method for electro-optically measuring the thickness of a container wall. A light source directs a light beam onto the outside surface of the container at an angle such that a portion of the light beam is reflected from the outside surface, and a portion is refracted into the container wall, reflected from the inside wall surface and then re-emerges from the outside wall surface. A lens system is disposed between a light sensor and the container wall for focusing onto the sensor light energy reflected from the outside and inside wall surfaces. The lens system has an image plane in which the sensor is disposed and an object plane collinear with the illumination light beam. The container is held in stationary position and rotated around its axis. An information processor scans the sensor at increments of container rotation, and determines wall thickness of the container between the inside and outside surfaces as a function of the separation between the points of incidence of the reflected light energies on the sensor. Although the apparatus and method disclosed in this patent again is well suited for measuring sidewall thickness of round containers, such apparatus and method are not well suited for measuring sidewall thickness of non-round containers inasmuch as the illumination beam cannot track undulations in the sidewall of a non-round container as the container rotates. It is a general object of the present disclosure to provide an apparatus and method for measuring sidewall thickness of non-round transparent containers.
The present disclosure embodies a number of aspects that can be implemented separately from or in combination with each other.
An apparatus for inspecting sidewall thickness of non-round transparent containers, in accordance with one aspect of the present disclosure, includes a conveyor for holding a container in stationary position and rotating the container around an axis. A light source directs light energy onto a sidewall of the container on the conveyor. An anamorphic lens system having a lens system axis directs onto a light sensor energy reflected from portions of the inside and outside surfaces of the container sidewall that are substantially parallel to the lens system axis. The term “substantially parallel” means that the surfaces of the container sidewall are parallel to the lens system axis within a narrow acceptance angle of the lens system, such as an acceptance angle of 1° in an exemplary embodiment of the disclosure. An information processor is responsive to the sensor for determining sidewall thickness at increments of container rotation as a function of separation at the sensor between light energies reflected from the inside and outside surfaces of the container sidewall.
An apparatus for inspecting sidewall thickness of non-round transparent containers, in accordance with another aspect of the present disclosure, includes a conveyor for presenting containers in sequence and holding each container in turn in stationary position while rotating the container around an axis. A light source directs light energy onto a sidewall of a container as it is held and rotated on the conveyor. An anamorphic lens system having a lens system axis directs onto a light sensor portions of the light energy reflected from inside and outside surfaces of the container sidewall in planes substantially perpendicular to the lens system axis. The term “substantially perpendicular” refers to light energy reflected in planes perpendicular to the lens system axis within a narrow acceptance angle of the lens system, such as 1° in an exemplary embodiment of the disclosure. The light energy portions reflected from inside and outside surfaces of the container sidewall in planes substantially perpendicular to the lens system axis sweep back and forth along the anamorphic lens system, as the container rotates, due to the non-roundness of the container. An information processor is responsive to the light sensor for determining sidewall thickness at increments of container rotation as a function of separation at the sensor between light energy portions reflected from the inside and outside surfaces of the container sidewall.
A method of inspecting sidewall thickness of a non-round container, in accordance with a further aspect of the present disclosure, includes holding the container in stationary position while rotating the container around an axis. A line-shaped light beam is directed onto a sidewall of the container, with the line-shaped light beam having a long dimension perpendicular to the axis of rotation. Portions of the light beam reflected from inside and outside surfaces of the container sidewall that are substantially perpendicular to light energy directed onto the container sidewall, as viewed from a direction parallel to the axis, are directed onto a light sensor. Container sidewall thickness is determined at increments of container rotation as a function of separation at the sensor between light energy portions reflected from the inside and outside surfaces of the container sidewall.